Buggy code:
private static final byte FLAG_VERSIONED = 2 ; private static final byte FLAG_VISIBLE = 1 ; private static Log log = LogFactory . getLog ( Component . class ) ; private AttributeModifier attributeModifiers = null ; private byte flags = ( ( Component . FLAG_VISIBLE ) | ( Component . FLAG_ESCAPE_MODEL_STRINGS ) ) | ( Component . FLAG_VERSIONED ) ; private String id ; private IModel model ; private MarkupContainer parent ; public static interface IVisitor { public static Object CONTINUE_TRAVERSAL = null ; public static Object STOP_TRAVERSAL = new Object ( ) ; public Object component ( Component component ) { } } public Component ( final String id ) { } public Component ( final String id , final IModel model ) { } public final Component add ( final AttributeModifier modifier ) { } public final void debug ( final String message ) { } public final void error ( final String message ) { } public final void fatal ( final String message ) { } public final MarkupContainer findParent ( final Class c ) { } public final MarkupContainer findParentWithAssociatedMarkup ( ) { } public final Application getApplication ( ) { } public final ApplicationPages getApplicationPages ( ) { } public final ApplicationSettings getApplicationSettings ( ) { } public final String getClassRelativePath ( ) { } public IConverter getConverter ( ) { } public final boolean getEscapeModelStrings ( ) { } public final FeedbackMessage getFeedbackMessage ( ) { } public String getId ( ) { } public final Locale getLocale ( ) { } public final Localizer getLocalizer ( ) { } public IModel getModel ( ) { } public final Object getModelLock ( ) { } public final Object getModelObject ( ) { } public final String getModelObjectAsString ( ) { } public final Page getPage ( ) { } public final IPageFactory getPageFactory ( ) { } public final String getPageRelativePath ( ) { } public final MarkupContainer getParent ( ) { } public final String getPath ( ) { } public final Request getRequest ( ) { } public final RequestCycle getRequestCycle ( ) { } public final Response getResponse ( ) { } public final Object getRootModelObject ( ) { } public Session getSession ( ) { } public final String getStyle ( ) { } public final boolean hasErrorMessage ( ) { } public final boolean hasFeedbackMessage ( ) { } public final void info ( final String message ) { } public boolean isAncestorOf ( final Component component ) { } public boolean isVersioned ( ) { } public boolean isVisible ( ) { } public final void modelChanged ( ) { } public final void modelChanging ( ) { } public final Page newPage ( final Class c ) { } public final Page newPage ( final Class c , final PageParameters parameters ) { } public void remove ( ) { } public final void render ( ) { } public void rendered ( ) { } public final boolean sameRootModel ( final Component component ) { } public final boolean sameRootModel ( final IModel model ) { } public final void setModel ( final IModel model ) { } public final void setModelObject ( final Object object ) { } public final void setRedirect ( final boolean redirect ) { } public final void setResponsePage ( final Page page ) { } public final Component setShouldEscapeModelStrings ( final boolean escapeMarkup ) { } public void setVersioned ( boolean versioned ) { } public final Component setVisible ( final boolean visible ) { } public String toString ( ) { } public final String urlFor ( final Class listenerInterface ) { } public final void warn ( final String message ) { } protected final void checkComponentTag ( final ComponentTag tag , final String name ) { } protected final void checkComponentTagAttribute ( final ComponentTag tag , final String key , final String value ) { } protected void detachModel ( ) { } protected final String exceptionMessage ( final String message ) { <START_BUG> return ( ( toString ( ) ) + "<seq2seq4repair_space>:<seq2seq4repair_space>" ) + message ; <END_BUG> } protected MarkupStream findMarkupStream ( ) { } protected final Page findPage ( ) { } protected IModel initModel ( ) { } protected void internalBeginRequest ( ) { } protected void internalEndRequest ( ) { } protected void internalOnBeginRequest ( ) { } protected void internalOnEndRequest ( ) { } protected void internalOnModelChanged ( ) { } protected void internalOnModelChanging ( ) { } protected void onBeginRequest ( ) { } protected void onComponentTag ( final ComponentTag tag ) { } protected void onComponentTagBody ( final MarkupStream markupStream , final ComponentTag openTag ) { } protected void onEndRequest ( ) { } protected void onModelChanged ( ) { } protected void onModelChanging ( ) { } protected abstract void onRender ( ) { } protected void redirectTo ( final Page page ) { } protected final void renderComponent ( final MarkupStream markupStream ) { } protected final void renderComponentTag ( ComponentTag tag ) { } protected final void renderComponentTag ( final MarkupStream markupStream ) { } protected final void replaceComponentTagBody ( final MarkupStream markupStream , final ComponentTag tag , final String body ) { } protected final Object visitParents ( final Class c , final Component . IVisitor visitor ) { } Component get ( final String path ) { } final boolean getFlag ( final int flag ) { } final void renderClosingComponentTag ( final MarkupStream markupStream , final ComponentTag openTag ) { } final void setFlag ( final byte flag , final boolean set ) { } final void setParent ( final MarkupContainer parent ) { } final boolean isAuto ( ) { } final void setAuto ( final boolean auto ) { } private final void detachModels ( ) { } private Object getRootModel ( final IModel model ) { } private final void setId ( final String id ) { } }

Fix:
return ( message + ":<seq2seq4repair_space>\n" ) + ( toString ( ) ) ;